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Local people fear that the fire may have contaminated the fish they normally eat

A gas-fuelled fire, with flames as high as 5m, may burn for months in waters off the Niger Delta in south-east Nigeria, Chevron has told the BBC.

Two workers died after January's explosion at the KS Endeavour exploration rig, owned by the US firm.

Friends of the Earth says this is the world's worst such accident in recent years.

Chevron spokesman Lloyd Avram says, despite the fire, the situation is now under control and no oil is leaking.

Nigeria is the largest oil producer in Africa.

Pouring cement

At the scene

By Mark LobelBBC News

Looking on, it was like watching a volcano erupting, fire spewing in every direction.

On a boat 50m from the fire, we saw black bubbles rise to the surface and black smoke spread into the air. Chevron had previously assured me there was no black smoke since the time a little fuel spilled just after the explosion in January.

Many people in Koluama, the community 10km away from the fire, are too afraid to eat fish, despite it being so crucial to their diets.

The new deputy state governor, on a visit of Koluama in Bayelsa State, was surprising critical of Chevron. He said the firm should have been better prepared for the accident. He told me he had seen signs of chemicals washing ashore.

A fire is burning in a 40m-wide area on the surface of the Atlantic Ocean, 10km off the Nigerian coast.

The company is trying to put out the fire by piercing a hole in the original gas well - through which cement will be poured.

"There'll be 10,000ft of drilling and interestingly we need to hit an area that is approximately 12sq inches," Mr Avram told the BBC.

"It is going to take some time, but I cannot predict how long that is going to be - conceivably months," he said.

Scientists are conducting tests to find out if local food and water has been contaminated by the gas in the ocean - after local people raised concerns.

Almost 100 people have left towns close to the fire and local chiefs are asking Chevron to relocate more.

A major build-up of gas pressure from drilling caused the explosion that set the rig on fire in the middle of January, according to the Nigeria's state run oil company.